I need some help

I’m getting this on my Derma Menu. I changed the GM:ShowHelp() function in garrysmod/gamemodes/sandbox/gamemodes/init.lua so it would open with my command. It opens once when I press F1 in the server and every time after that it says,

Unknown Command: ‘OpenDerma’

Can you help me with this

Thanks,
Th3SiNz